Unstable air along a pressure trough well ahead of a cold front over the Ohio River Valley sparked scattered thunderstorms during the afternoon and evening hours. Localized wind damage was reported in northern Maryland, and a considerably severe thunderstorm affected parts of the central Shenandoah Valley in Virginia.
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The episode as NWS LWX wrote it up.
Unstable air along a pressure trough well ahead of a cold front over the Ohio River Valley sparked scattered thunderstorms during the afternoon and evening hours. Localized wind damage was reported in northern Maryland, and a considerably severe thunderstorm affected parts of the central Shenandoah Valley in Virginia.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Baltimore/Washington wrote its last area forecast discussion before the first event at Jul 6, 9:28 AM EST, 3 hours 42 minutes earlier.
Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1028 AM EDT Thu Jul 6 2023 .SYNOPSIS... A weak trough both at the surface and aloft will remain overhead through today while high pressure remains over the Atlantic. A cold front will approach from the west Friday and it will likely stall to our west through Saturday, bringing unsettled conditions to our area. The cold front may finally push through Sunday with weak high pressure settling overhead early next week. && .NEAR TERM /THROUGH TONIGHT/... Mid-morning update: 12z IAD sounding shows very weak flow through the depth of the troposphere, with a mean wind of only 1 knot through the lowest three kilometers, and only 4 knots through the depth of the cloud bearing layer. There also aren't any real surface boundaries of note, although there is a weak surface trough analyzed by WPC just to our south across the Northern Neck of Virginia. With the weak steering flow and lack of discernible boundaries, terrain circulations and bay/river breezes will serve as the foci for convective initiation this afternoon. This morning's sounding showed a precipitable water value of 1.8 inches, so storms today could produce heavy rainfall. With the weak steering flow, storms will also be slow moving to stationary. So with nearly stationary storms producing heavy rainfall, a few localized instances of flooding can't be ruled out, especially with any storms that go up along the bay/river breeze within the urban corridor. With the lack of shear and low-level boundaries to maintain sustained convergence, storms should be rather disorganized and short lived, which should act as a limiting factor for flooding potential. Any thunderstorm activity should quickly dissipate this evening with loss of daytime heating. Previous discussion follows... Isolated to scattered showers and thunderstorms are expected today, primarily in the afternoon and evening hours. However, recent CAMs have been trending earlier with the initiation of convection, so could see showers and tstorms kick off earlier this afternoon. Steering flow is expected to be very light today, so showers and thunderstorms will be driven by terrain and boundaries from outflows and bay and river breezes. As a result, some storms may be slow moving, resulting in isolated flooding in sensitive locations. After convection dissipates this evening, similar muggy conditions to last night are expected with possible patchy fog. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Heading into the weekend, the CONUS will be transitioning to a more meridional pattern as an upper trough digs southward into the Great Lakes and Northeast. As an associated cold front approaches the area, convection may be more widespread on Friday. Weak ridging behind an exiting disturbance may act to reduce coverage, however, latest CAMs seem in favor of a round of heavier showers and thunderstorms. The front may linger in the region over the weekend, acting as a focus for convection during the afternoon and evening hours as one or two shortwaves also pass through. Above normal PWs with multiple rounds of precip could continue to bring periods of heavy rain to the area, and isolated flooding may be possible. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Current guidance points to Sunday being the most active day of the period as a boundary lingering across the area and a shortwave trough passing through, possibly spawning an area of surface low pressure along the front. Shear increases a bit with the trough, so there could be some stronger storms. However, abundant cloud cover and a very moist atmosphere (precipitable water values around 2 inches) point to a threat of heavy rain, especially if convection focuses repetitively along the slow moving boundary. High temperatures likely drop a little below normal due to the clouds. On Monday, the boundary may drop slightly to the south, but another shortwave trough may cross during this time. Current forecast has PoPs in the 40-50 percent range, but this will be dependent on the frontal position. For Tuesday and Wednesday, guidance has the Mid Atlantic in between boundaries stretched across the southeast US and Great Lakes. While subtle forcing features could result in an isolated shower or storm, these days should be mainly dry. Temperatures will return to typical July values, although dew points/humidity will be a bit lower than over the weekend. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... VFR conditions are expected overall today, but restrictions are possible with any showers and thunderstorms. Brought the timing of convection a few hours earlier based on the CAMs, to around 17-21z (18-22z for BWI/MTN). Similar to last night, muggy conditions may result in patchy fog overnight, especially at locations that receive precip during the day. The same summerlike pattern of broadly VFR with diurnal showers and thunderstorms causing brief reductions is expected to continue Friday and Saturday. Convection may be more widespread Friday and Saturday with a passing cold front. Showers and thunderstorms are likely Sunday, perhaps in multiple rounds. A chance of thunderstorms will continue on Monday but will be dependent on the position of a slow moving front. A period of sub- VFR ceilings can't be ruled out. && .MARINE... Winds are expected to remain below SCA criteria today and Friday, though showers and thunderstorms over the waters may bring localized stronger wind gusts. Coverage of storms will be limited over most of the waters today, but portions of the lower tidal Potomac and the eastern Chesapeake Bay may see more showers and thunderstorms. SCAs may be necessary Saturday and Sunday with a passing cold front and southerly winds increase over the waters. Southerly winds ahead of a front may result in marginal SCA conditions on Sunday. Thunderstorms will also be likely. Winds may become lighter Monday as the front slowly moves through, although the chance for thunderstorms will continue. && .TIDES/COASTAL FLOODING... A light onshore to south flow is most likely through the end of the week. This will cause elevated water levels around times of high tide. The most likely scenario is for many areas to reach action stages. However, minor tidal flooding cannot be ruled out, especially at sensitive locations like Straits Point, Annapolis, and DC SW Waterfront. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && SYNOPSIS...CJL NEAR TERM...KJP/CAS SHORT TERM...CAS LONG TERM...ADS AVIATION...ADS/CAS MARINE...ADS/CAS TIDES/COASTAL FLOODING...ADS
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 1059 AM EDT Thu Jul 6 2023 ANZ530>543-DCZ001-MDZ008-011-013-014-016>018-504-506-508- VAZ053>057-527-071500- Chesapeake Bay north of Pooles Island MD- Chesapeake Bay from Pooles Island to Sandy Point MD- Chesapeake Bay from Sandy Point to North Beach MD- Chesapeake Bay from North Beach to Drum Point MD- Chesapeake Bay from Drum Point MD to Smith Point VA- Tidal Potomac from Key Bridge to Indian Head MD- Tidal Potomac from Indian Head to Cobb Island MD- Tidal Potomac from Cobb Island MD to Smith Point VA- Patapsco River including Baltimore Harbor- Chester River to Queenstown MD-Eastern Bay- Choptank River to Cambridge MD and the Little Choptank River- Patuxent River to Broomes Island MD- Tangier Sound and the inland waters surrounding Bloodsworth Island-District of Columbia-Cecil-Southern Baltimore- Prince Georges-Anne Arundel-Charles-St. Marys-Calvert- Central and Southeast Montgomery-Central and Southeast Howard- Southeast Harford-Fairfax-Arlington/Falls Church/Alexandria- Stafford-Spotsylvania-King George- Central and Southeast Prince William/Manassas/Manassas Park- 1059 AM EDT Thu Jul 6 2023 This Hazardous Weather Outlook is for the Maryland portion of the Chesapeake Bay, Tidal Potomac River, and I-95 corridor through central Maryland, northern Virginia, and District of Columbia. .DAY ONE...Today and Tonight Thunderstorms will be capable of producing locally heavy rainfall this afternoon, which could cause an isolated instance of flooding, mainly in sensitive urban and suburban areas. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Thunderstorms will be capable of producing locally heavy rainfall Sunday afternoon into Sunday night, which could cause scattered instances of flooding or flash flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. MDZ003>006-503-505-507-VAZ025>031-036>040-050-051-501-502-505>508- 526-WVZ050>053-055-071500- Washington-Frederick MD-Carroll-Northern Baltimore- Northwest Montgomery-Northwest Howard-Northwest Harford-Augusta- Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke-Nelson- Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper- Northern Fauquier-Southern Fauquier-Western Loudoun- Eastern Loudoun-Northern Virginia Blue Ridge- Central Virginia Blue Ridge-Northwest Prince William-Hampshire- Morgan-Berkeley-Jefferson-Hardy- 1059 AM EDT Thu Jul 6 2023 This Hazardous Weather Outlook is for portions of eastern West Virginia, northern and central Virginia, and central and western Maryland. .DAY ONE...Today and Tonight Thunderstorms will be capable of producing locally heavy rainfall this afternoon, which could cause an isolated instance of flooding. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Thunderstorms will be capable of producing locally heavy rainfall Sunday afternoon into Sunday night, which could cause scattered instances of flooding or flash flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. MDZ001-501-502-VAZ503-504-WVZ501>506-071500- Garrett-Extreme Western Allegany-Central and Eastern Allegany- Western Highland-Eastern Highland-Western Grant-Eastern Grant- Western Mineral-Eastern Mineral-Western Pendleton- Eastern Pendleton- 1059 AM EDT Thu Jul 6 2023 This Hazardous Weather Outlook is for the Allegheny Front counties in western Maryland, eastern West Virginia, and Highland County Virginia. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Thunderstorms will be capable of producing locally heavy rainfall Sunday afternoon, which could cause isolated instances of flooding or flash flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Sterling radar (KLWX), 58 km away, was scanning. The volume nearest the first event began at 18:09 UTC.
1 thunderstorm wind. Local standard time, as filed.
Several trees and branches blew down near Watersville, including near the intersection of Flag Marsh Road and Watersville Road, Watersville Road and Gillis Falls Road, and Gillis Ford Road and John Pickett Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2023Every state in 2023This day in weather historyWarnings in Maryland, July 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1107673.